Totally @monmart. We’re working on adding a media query for 1200px that’s inside in the UI soon. Thanks for the request!
What you can do for now is add this to your Custom Code tab (in your site settings) <head> field or add it to the bottom of webflow.css after export.
<style type="text/css">
@media screen and (min-width: 1200px) {
.w-container {
max-width: 1170px;
}
}
</style>